The invention described herein may be manufactured, used and licensed by or for the United States Government.
This invention relates to reactive sorbents and methods of making and using the same for the decontamination of surfaces contaminated with highly toxic materials, including chemical warfare (xe2x80x9cCWxe2x80x9d) agents and/or industrial chemicals, insecticides, and the like. More particularly, the invention relates to improvement of surface decontamination processes and reagents by the development of novel sorbents and sorbent preparation methods, including compositions comprising sodium zeolite (NaY) and silver exchanged zeolite (AgY).
Exposure to toxic agents, and especially CW agents, and.related toxins, is a potential hazard to the armed forces and to civilian populations, since CW agents are stockpiled by several nations, and other nations and groups actively seek to acquire these materials. Some commonly known CW agents are bis-(2-chloroethyl) sulfide (xe2x80x9cHDxe2x80x9d or mustard gas), pinacolyl methylphosphonofluoridate (xe2x80x9cGDxe2x80x9d), 0-ethyl S-(2-diisopropyamino)ethyl methylphosphonothiolate (xe2x80x9cVXxe2x80x9d), and isopropyl methylphosphonofluoridate, or Sarin (xe2x80x9cGBxe2x80x9d) as well as analogs and derivatives of these agents. Although originally introduced in WWI, mustard gas has been used in recent times, as have the newer and more deadly nerve agents VX and GB (Zurer, 1998, Chem. and Eng. News 76: 7; Black, et al., 1994 J. Chromatogr. A 662: 301-321; Black, et al., 1993 J. Chromatogr. A 637: 71-80; Rouhi, 1999 Chem. and Eng. News 77: 37; Ember, Chem. and Eng. News 76: 6-7).
These CW agents are generally delivered as fine aerosol mists which, aside from presenting an inhalation threat, will deposit on surfaces of military equipment and hardware, including uniforms, weapons, vehicles, vans and shelters. Once such equipment and hardware is contaminated with one of the previously mentioned highly toxic agents, the agent must be removed in order to minimize contact hazards.
For this reason, there is an acute need to develop and improve technology for decontamination of highly toxic materials. This is especially true for the class of toxic materials known as nerve agents or nerve gases that are produced and stockpiled for both industrial use and as CW agents. Simply by way of example, one class of nerve agents with a high level of potential lethality is the class that includes organophosphorus-based (xe2x80x9cOPxe2x80x9d) compounds, such as Sarin, Soman, and VX. Such agents can be absorbed through inhalation and/or through the skin of an animal or person. The organophosphorus-type (xe2x80x9cOPxe2x80x9d) CW materials typically manifest their lethal effects against animals and people by inhibiting acetylcholine esterase (xe2x80x9cAChExe2x80x9d) enzyme at neuromuscular junctions between nerve endings and muscle tissue to produce an excessive buildup of the neurotransmitter acetylcholine, in an animal or person. This can result in paralysis and death in a short time.
CW agents and related toxins are so hazardous that simulants have been developed for purposes of screening decontamination and control methods. These simulants include, e.g. 2-chloroethylphenyl sulfide (CEPS), an HD simulant, dimethyl methylphosphonate (DMMP), a G-agent simulant, and O,S-diethyl phenylphosphonothioate (DEPPT) a VX simulant.
One approach to cleanup and decontamination of the highly toxic agents is to develop various types of sorbents to trap and hold the CW agents to facilitate their removal. For example, the U.S. Army uses a nerve agent decontamination solution, DS2, which is composed (by weight) of 2% NaOH, 28% ethylene glycol monomethyl ether, and 70% diethylenetriamine (Richardson, G. A. xe2x80x9cDevelopment of a package decontamination system,xe2x80x9d EACR-1 310-17, U.S. Army Edgewood Arsenal Contract Report (1972), incorporated by reference herein). Although this decontamination solution is effective against OP nerve agents, it is quite toxic, combustible, highly corrosive, and releases toxic by-products into the environment.
Another decontamination material, used as an alternative to DS2, is XE555 sorbent (Ambergard(trademark) Rohm and Haas Company, Philadelphia, Pa.). XE555 is presently being used by the military for immediate decontamination applications. However, XE555 has several disadvantages. Although effective at removing chemical agents, XE555 does not possesses sufficient reactive properties to neutralize the toxic agent(s) picked up by this sorbent. Thus, after use for decontamination purposes, XE555 itself presents an ongoing threat from off-gassing toxins and/or vapors mixed with the sorbent.
It would be desirable to have a sorbent that is reactive, which degrades or decontaminates the toxic agent after adsorbing or absorbing the agent. There are reports that such xe2x80x9creactive sorbentsxe2x80x9d are being developed for the decontamination of chemical warfare agents, including those by, Yang, Y. -C., et al. 1992 Chem. Rev., 92;1729-1743; Yang, Y. -C., 1995 Chem. Ind., 334-337; Ekerdt, et al., 1988, J. Phys. Chem. 92: 6182-6188; Wagner, et al., 1999 J. Phys. Chem. B, 103; 3225-3228; Spafford, R. B. The Development of a Reactive Sorbent for Immediate Decontamination, ERDEC-CR-218, U.S. Army ERDEC: Aberdeen Proving Ground, Md., 1996.
However, to date, none of these reports has described a useful and effective reactive sorbent for the most toxic CW agents, such as VX, HD and GD.
Chemical reactions for neutralizing CW agents are known, although they have not proved useful for decontamination. For example, it has been shown that VX and HD decompose on sorbents impregnated with AgF (Ekerdt, et al, 1988, J. Phys. Chem. 1988, 92:6182-6188) and gaseous HD decomposes on 13X zeolite (Bellamy, 1994, J. Chem. Soc. Perkin Trans. 2:2325-2328). AgF is currently used to transform VX vapor into its more volatile G-analog, ethyl methylphosphonofluoridate, to facilitate its detection by air monitoring equipment (Spafford, 1996, xe2x80x9cThe Development of a Reactive Sorbent for Immediate Decontamination,xe2x80x9d ERDEC-CR-218, U.S. Army ERDEC: Aberdeen Proving Ground, Md.). This reaction is not useful for decontamination purposes, because corrosive HF byproduct also forms, although the reaction mechanism is apparently not completely known (Spafford, 1996, Id.).
For HD vapor on 13X zeolite, Bellamy, 1994 (J. Chem. Soc. Perkin Trans. 2:2325-2328) tentatively assigned a product detected by 13C MAS NMR to the sulfonium ion CHxe2x80x94TG. CHxe2x80x94TG is formed from the chlorohydrin (CH) and thiodiglycol (TG) hydrolysis products of HD (Yang, Y. -C. et al., 1988, J. Org. Chem. 53:3293-3297). The predominate formation of CHxe2x80x94TG from HD sorbed in soil by 13C MAS NMR has similarly been reported (Wagner et al., 1998, Langmuir 14:6930-6934). This pathway is illustrated by the following reaction scheme. (see Yang, et al., 1988, J. J. Ore. Chem. 53:3293-3297). 
Although a number of metal ions are known to catalyze G-agent hydrolysis (Courtney, et al., 1957 Am. Chem. Soc. 79:3030-3036; Epstein, et al., 1958 J. Am. Chem. Soc. 80:3596-3598), with the possible exception of the AgF reaction, demonstrative examples of metal-catalyzed hydrolysis of VX appear to be lacking (Yang, Y. -C. 1999, Acc. Chem. Res. 32:109-115). Indeed, in perhaps the sole example, the hydrolysis of VX in buffered solutions of TMEN [N,N,Nxe2x80x2,Nxe2x80x2-tetrariethylethylenediamine] copper (II) complexes (Albizo, et al., 1987, In Proceedings of the 1986 CRDEC Scientific Conference on Chemical Defense Research, Vol. I, CRDEC-SP-87008, U.S. Army CRDEC: Aberdeen Proving Ground, Md., pp. 105-109), it is speculated that catalysis may be inhibited by competing complexation of the diisopropylamino group of VX (Yang, et al., 1992, Chem. Rev., 92:1729-1743).
Silver possesses a strong affinity for the complexation of sulfur-containing ligands (Cotton, et al., 1988, In Advanced Inorganic Chemistry, 5th ed., John Wiley and Sons, New York, pp. 942-943), and Ag+ has been shown to promote the hydrolysis of diethyl ethylphosphonothioate (Saville, B. 1957 xe2x80x9cCation Assisted Nucleophilic Displacements on Phosphorus, Porton Technical Paper No. 608,xe2x80x9d Chemical Defense Experimental Establishment: Porton Down, UK, [unclassified]).
Despite these reports, there remains a need in the art for even more effective compositions and methods for detoxifying CW agents.
In order to solve these and other problems in the art, the present invention provides the novel compositions suitable for use as xe2x80x9creactive sorbentsxe2x80x9d and methods for preparing and using these novel reactive sorbents to decontaminate a wide range of highly toxic materials. The reactive sorbents of the invention are, for example, based on the interaction of a silver-exchanged zeolite (AgY) or sodium zeolite (NaY) with the sulfur-containing agents VX and HD.
In a first embodiment, the invention broadly provides a method of detoxifying chemical warfare agents, by a process including the steps of: contacting a material that includes, or potentially includes, at least one toxic agent, e.g., a chemical warfare agent, with a quantity of silver zeolite sufficient for reacting substantially all of the toxic agent to produce at least one derivative that is substantially nontoxic, relative to the toxic agent.
Preferably, the silver zeolite or sodium zeolite is present for a time ranging from about 1 minute to about 60 days, and at a temperature ranging from about xe2x88x9230xc2x0 C. to about 50xc2x0 C. It is also preferred that the silver zeolite have a silver content ranging from about 10 to about 40% wt/wt, and that it is in a form suitable for application to objects, surfaces and such, as required.
Suitable forms for applying silver zeolite or sodium zeolite include, for instance, a powder, pellets, a granulate, a slurry comprising a silver zeolite powder suspended in a compatible solvent, and/or combinations thereof. The term, xe2x80x9ccompatible solventxe2x80x9d should also be understood to include both polar and nonpolar solvents, such as organic solvents, as well as optional miscibility enhancers such as, e.g., detergents, surface active agents, and the like. A compatible solvent is also preferably selected to be miscible with the toxic material and/or any carriers, solvents and/or polymers included with the toxic material.
The inventive methods are preferably applied to treat and substantially decontaminate such toxic. agents as: bis-(2-chloroethyl) sulfide; 0-ethyl S-(2-diisopropylamino)ethyl methylphosphonothiolate; pinacolyl methylphosphonofluoridate; isopropyl methylphosphonofluoridate, and/or combinations thereof.
It has also been determined that employing the methods of the invention, the breakdown products of bis-(2- chloroethyl) sulfide include thioxane, and the breakdown products of O-ethyl S-[2-diisopropylethylamino] methylphosphonothiolate) include O-[2-diisopropylethylamino] O-ethyl methylphosphonate. In addition, the breakdown products of 0-ethyl S-(2-diisopropylamino)ethyl methylphosphonothiolate and/or pinacolyl methylphosphonofluoridate, include phosphonates.
The toxic agent or material, e.g., the chemical warfare agent, is optionally present in liquid and/or vapor form. When the toxic agent to be treated is in liquid form, the liquid can be on a surface, and optionally further includes a polymer that renders the chemical warfare agent as a viscous gel material. Under field conditions, i.e., where highly toxic agents have been applied to the ground, buildings, vehicles, etc., deliberately or by accident, the concentrations will optionally range from, for instance, less than 0.1 gram/meter2 (g/m2) to 15 g/m2. When the toxic material is a liquid or solid, e.g., pesticides, the liquid can be on a surface, and further is optionally a component within a compatible solvent, e.g., lactones, ethers, alcohol, hydrocarbons and mixtures thereof. The toxic material is sometimes mixed with a polymer that is present, e.g. in a concentration ranging from about 1.0 percent by weight to about 10 percent by weight. Thus, the chemical warfare is present in such toxic material in a concentration ranging from about 90 percent by weight to about 99 percent by weight.
The methods of the invention are readily applied to toxic agents, e.g., chemical warfare agents, in an industrial setting for disposal of such agents. The methods of the invention are also optionally applied to materials that are contaminated, or potentially contaminated that include, e.g., an article of manufacture, a solid composition, a liquid composition, a vapor or gas composition, and combinations thereof. In particular, the methods of the invention are readily applied to contaminated or potentially contaminated items such as, e.g., a vehicle, a weapon or weapon system, pavement, soil, vegetation, a garment, a tent, a building and/or combinations thereof.